Yarn gripper for yarn-testing machines and the like

ABSTRACT

A YARN GRIPPER FOR YARN-TESTING MACHINES AND THE LIKE, FOR TESTING INDIVIDUAL YARN LENGTHS IN STAGES, INCLUDES A FIRST GRIPPING JAW HAVING A CONICAL GRIPPING SURFACE AND A SECOND GRIPPING JAW HAVING A HOLLOW SURFACE COMPLEMENTARY TO THE SURFACE OF THE FIRST GRIPPING JAW, THE TWO GRIPPING JAWS BEING COAXIAL AND AXIALLY DISPLACEABLE RELATIVE TO EACH OTHER. THE YARN ENTERS AND ANNULAR GAP TANGENTIALLY OF THE CONICAL GRIPPING SURFACES IN THE DIRECTION OF   A TANGENT TO THE CONICAL SURFACE AND WITHOUT ANY SUDDEN CHANGES IN DIRECTION. THE END FACE OF THE SECOND GRIPPING JAW MAY BE DESIGNED TO FUNCTION DIRECTLY AS A YARNGUIDE, AND ADJUSTABLE GUIDE MEANS CAN BE PROVIDE TO ENABLE THE SIZE OF THE LOOP INSIDE THE ANNULAR GAP TO BE VARIED.

Nov. 1971 P ls ETAL 3,618,373

YARN GRIPPER FOR YARN-TESTING MACHINES AND THE LIKE Filed Oct. 8, 1969 IN ME N T'ORS 94-8 61?? P5. 1. ammo Rom HTTQR ME VS 3,618,373 YARN GRIPPER F OR YARN-TESTING MACHINES AND THE LIKE Albert Peisl, Uster, and Gerold Roos, Esslingen, Switzerland, assignors to Zellweger Ltd., Uster, Switzerland Filed Oct. 8, 1969, Ser. No. 864,831

Claims priority, application Switzerland, Nov. 8, 1968,

16,677/ 68 Int. Cl. G01n 3/04 U.S. Cl. 73-103 9 Claims ABSTRACT OF THE DISCLOSURE A yarn gripper for yarn-testing machines and the like, for testing individual yarn lengths in stages, includes a first gripping jaw having a conical gripping surface and a second gripping jaw having a hollow surface complementary to the surface of the first gripping jaw, the two gripping jaws being coaxial and axially displaceable relative to each other. The yarn enters an annular gap tangentially of the conical gripping surfaces in the direction of a tangent to the conical surface and without any sudden changes in direction. The end face of the second gripping jaw may be designed to function directly as a yarnguide, and adjustable guide means can be provided to enable the size of the loop inside the annular gap to be varied.

BACKGROUND OF THE INVENTION The purpose of yarn grippers for yarn-testing machines is to hold the yarn to be tested so firmlythat the yarn is unable to slip through the grippers under strain. On the other hand, however, it is important that the yarn should not be damaged in any way by the gripping effect, which 3 would result, generally, in the yarn breaking in the gripping Zone. The results of testing are adversely affected both by slipping of the yarn through the grippers and by yarn failure, so that the test results are useless.

Conventional yarn grippers consist, essentially of two flat circular surfaces which grip the yarn when they are pressed toward each other, for example by a powerful spring. For gripping different yarn materials, it is necessary to select suitable materials for the actual gripping surfaces in each case, to obtain the most favorable friction conditions. The gripping pressure exerted on the grippers by the spring cannot be increased arbitrarily, because the spring loading has to be overcome in order to open the gripper and suitably resistant gripper components have to be used. The motive power available also has to be suflicient to actuate the gripper.

' The strain which a conventional yarn gripper is likely to encounter thus has limits imposed on it by all these conditions, so that any increase in the measuring range for the yarn is governed by the development of a suitable yarn gripper.

SUMMARY OF THE INVENTION This invention relates to yarn grippers for yarn-testing machines and the like and, more particularly, to an improved yarn gripper whose gripping surfaces have contours such that the yarn, in the gripping zone, follows a three-dimensional path along the gripping surfaces.

The objective of the invention is to provide an improved yarn gripper for yarn-testing machines and the like, for testing individual yarn lengths in stages. The yarn enters an annular gap tangentially of a conical gripper member in the direction of a tangent to the conical surface thereof and without any sudden changes in direction. The yarn travels in annular gap along a line substantially corresponding to the shortest distance between the yarn inlet United States Patent O and the yarn outlet. In doing so, the yarn describes an are which produces an additional gripping effect.

The conical member preferably is displaceable axially to a limited extent relative to a conical sleeve providing another gripper member. Since the inserted yarn is in contact with the conical sleeve only around approximately one quarter of its circumference, the opposite gene'ratrix of the conical member is applied to generating the conical surface of the conical sleeve. The end face or end edge of the conical sleeve may be designed to function directly as a yarn guide, and its surface accordingly is polished so that the yarn can be guided into the annular gap without any damage.

Additional adjustable guide means can be provided in order, for example, to enable the size of the yarn loop inside the annular gap to be varied.

An object of the invention is to provide an improved yarn gripper for yarn-testing machines.

Another object of the invention is to provide such a yarn gripper including yarn gripper jaws having cooperating conical yarn gripping surfaces.

A further object of the invention is to provide such a yarn gripper in which the yarn is held between two gripping surfaces in a manner such that it follows a threedimensional path along the gripping surfaces.

Another object of the invention is to provide such a yarn gripper in which the yarn enters an annular gap tangentially of a conical gripper member in the direction of the tangent to the conical surface and without any sudden changes in direction.

A further object of the invention is to provide such a yarn gripper including adjustable guide means enabling the size of the loop inside the annular gap to be varied.

For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is an exploded perspective view of a yarn gripper embodying the invention;

FIG. 2 is a longitudinal or axial sectional view through the yarn gripper showing the latter in a closed condition;

FIG. 3 is a view similar to FIG. 2 showing the yarn gripper in the open position;

FIG. 4 is an end elevation view of the yarn gripper; and

FIG. 5 is a side elevation view of the yarn gripping zone.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the illustrated embodiment of the invention includes a screw 1 extending through a cap 2 which is seated in a conical recess in the outer face of a conical member 3. Conical gripping member 3 terminates, at the apex of its conical or frusto-conical surface, in two claws 31, and rests, with some play, on the cylindrical end of a bolt 4. In position on bolt 4, claws 31 of conical member 3 engage flat surfaces 41 of a collar 42 in such a manner that, in spite of the loose fit of conical member 3 on bolt 4, the conical member cannot be turned relative to bolt '4.

Beyond collar 42, bolt 4 has a cylindrical shaft 43 which is embraced by a closure spring 6, shaft 43 terminating in a piece 5, as best seen in FIGS. 2 and 3. The left hand end of bolt 4, as viewed in the drawings, has an internally threaded recess 7 receiving screw 1. Components 1, 2, 3, 4 and 5 form the movable part of the yarn gripper, and are mounted concentrically and coaxially in a sleeve 11 formed with a conical recess 12.

The smaller end of conical recess 12 has the same cone angle as the cone angle of conical member 3, and recess 12 also has a conical surface 13, near its outer edge, and having a slightly larger cone angle. Thereby, an outwardly diverging gap is formed between the conical surface 13 and the conical member 3. The yarn 10 is guided through this gap. To reduce friction between yarn 10 and conical sleeve 11, inlet edge 14 of conical recess 12 is polished and correspondingly rounded. Edge 14 is stepped, along one sector 15, in order to insert the yarn exactly into the concentric annular gap and to avoid sudden changes in the direction of travel of the yarn. In this manner, yarn can be inserted into the annular gap tangentially to the conical sleeve and the gripping point is determined by the step 16 in the inlet edge 14.

FIG. 2 illustrates the yarn gripper after it has been assembled and closed. Collar 42 of bolt 4 is guided in a corresponding axial passage or bore in conical sleeve '11, and sleeve 11 is widened, toward its rear end, to form a spring housing for spring 6. One end of spring 6 engages a surface or shoulder 17, at this widened portion, and the other end engages end piece 5.

Actuation of the yarn gripper also is diagrammatically illustrated in FIG. 2. A vertically displaceable cam 20 has a lower cam surface 21 and an upper cam surface 22 which act upon the end piece of bolt 4 through a plunger 19. If cam 20 is moved vertically downwardly, plunger 19 is lifted off the lower cam surface 21 on to upper cam surface 22, and thus presses bolt 4 to the left against the bias of spring 6. The result is that the annular gap between conical member 3 and conical surface 1213 is opened, as illustrated in FIG. 3.

In FIGS. 4 and 5, which are respectively front end elevation and side elevation views, the path followed by the inserted yarn is shown in an approximate form. The path describes an are directed toward the tip of the cone, without undergoing a sudden change in direction. The depth of stepped sector is such that yarn 10 does not have any tendency to slide off toward claws 31, but always remains on the surface of conical member 3.

A guide segment 18, arranged concentrically on cylindrical sleeve 4, controls the looping angle which yarn '10 forms with conical member 3, from the point at which it enters the gripping zone to the point at which it leaves on the sector 15. Guide segment .18 is rotatably displaceable relative to cylindrical sleeve 4, so that its run-01f edge 23 can be adjusted to correspond to the required looping angle.

The gripping pressure can be increased further by limiting the wall thickness of either the conical member or of the sleeve to such an extent that the gripping surfaces are resiliently deformed by the yarn gripped between the conical surfaces. This enlarges the gripping zone in which the yarn is held in the yarn gripper.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A yarn gripper for yarn-testing machines and the like, for testing individual yarn lengths in stages, said yarn gripper comprising, in combination, two gripping members providing a pair of cooperating yarn gripping surfaces forming a gripping zone and having contours such that the yarn, in the gripping zone, follows a threedimensional path along said gripping surfaces, said gripping members comprising a first gripping jaw including a substantially frusto-conical first gripping surface, a second gripping jaw including an axially extending sleeve having a recess in one end and a bore extending axially from said recess, said recess having a frusto-conical second gripping surface complementary to said first gripping surface, and means positioned within said sleeve and secured to said first gripping jaw for biasing said first gripping jaw into said recess and biasing said first and sec- 4 ond gripping surfaces together, said means arranged to afford axial displacement of said first gripping jaw within said recess.

2. A yarn gripper for yarn-testing machines and the like, as set forth in claim 1, characterized in that the second gripping surface in said recess having an inner part spaced from the end of said sleeve and an outer part extending from the inner part to the end of said sleeve, the inner part of said second gripping surface having the same cone angle as that of said first gripping surface on said gripping jaw, and the outer part of said second gripping surface having a cone angle somewhat larger than the cone angle of said first gripping surface and thereby defining an outwardly divergent gap between said first gripping surface and said second gripping surface.

3. A yarn gripper for yarn-testing machines and the like, as set forth in claim 1, characterized in that said sleeve forms a spring housing at the opposite end thereof from said recess, said means for biasing said first and second gripping surfaces together comprises an axially extending bolt secured at one end to said first gripping jaw and extending therefrom through said sleeve, a spring positioned within said housing about said bolt and acting on said bolt and the spring housing for biasing said first gripping jaw into said recess.

4. A yarn gripper for yarn-testing machines and the like, as claimed in claim 1, in which said first gripping jaw is loosely mounted on a bolt extending coaxially through said sleeve; and means pressing said first gripping jaw into said recess in a self-aligning manner.

5. A yarn gripper for yarn-testing machines and the like, as claimed in claim 4, in which said means pressing said first gripping jaw comprises a cap engaged with the outer surface of said first gripping jaw and a screw engaged through said cap and threaded into said bolt.

6. A yarn gripper for yarn-testing machines and the like, as claimed in claim 5, in which that portion of said sleeve facing away from said recess has an enlarged axial recess therein forming an extension of the axial bore receiving said bolt, the intersection of said axial bore and said axial recess providing a shoulder; an end member secured to said bolt and disposed in said axial recess; and a spring embracing said bolt between said end mernber and said shoulder.

7. A yarn gripper for yarn-testing machines and the like, as claimed in claim 6, in which the outer peripheral edge of said recess having said frusto conical second gripping surface is rounded to reduce friction with the am. y 8. A yarn gripper for yarn-testing machines and the like, as claimed in claim 7, including a substantially cylindrical guide segment angularly displaceably mounted on said sleeve adjacent said recess having said frusto conical second gripping surface; said guide segment having a run-off edge adjustable to the required looping angle for the yarn by angular displacement of said guide segment.

9. A yarn gripper for yarn-testing machines and the like, as claimed in claim 1, in which at least one of said first and second gripping jaws is resiliently deformable to provide a larger gripping zone for the yarn.

A Symposium on Internal Combustion Engine Valves, published by Thompson Products, Inc., Cleveland, Ohio, received October 1958, p. 127, T] 789 T5.

JERRY W. MYRACLE, Primary Examiner US. Cl. X.Ri 73'===95.5 

